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Enhanced Engine Braking Strategy

IP.com Disclosure Number: IPCOM000007442D
Publication Date: 2002-Mar-26
Document File: 5 page(s) / 46K

Publishing Venue

The IP.com Prior Art Database

Abstract

This strategy is intended to provide immediate clutch response sufficient to prevent slip during engine braking, yet permit smooth off-throttle operation by eliminating torque transfer during events where slip is unlikely. Additionally, the strategy should be able to optimize the clutch response required to control slip to minimize clutch application during front overrun events. Finally, it is intended to ensure front overrun control at low speeds where previous strategies would disconnect to account for turns

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Enhanced Engine Braking Strategy

Introduction:

This strategy is intended to provide immediate clutch response sufficient to prevent slip during engine braking, yet permit smooth off-throttle operation by eliminating torque transfer during events where slip is unlikely. Additionally, the strategy should be able to optimize the clutch response required to control slip to minimize clutch application during front overrun events. Finally, it is intended to ensure front overrun control at low speeds where previous strategies would disconnect to account for turns.

Description:

The strategy boosts the clutch to a level determined by speed, throttle position and engine rpm (message $201, Byte 1&2).

Engine Braking Clutch Duty Cycle = f[vehicle_speed, throttle_position, engine_rpm]

The function is as follows:

If (throttle_position) £ eb_throttle_switchpoint

{

                    If (vehicle_speed £ eb_bind_speed_switchpoint

                    {

                    Follow Regime A                                      ‘For lower speeds

                    }

                    Else

{

                    Follow Regime B                                      ‘For higher speeds

                    }

}

Else

{

                    output_clutch_DC = 0

}


Regime A (For low speeds)

Determine what clutch to output for the given rpm

output_clutch_DC = f[start_apply_rpm, rpm]

If (rpm £ eb_start_apply_AB_rpm) or (iSWA > eb_iSWA_threshold)

{

output_clutch_DC = 0                    ‘No response for turns or low rpm

                    ‘ Note slip responses for front overrun should be retained for turns

}

else

{

if (output_clutch_DC  > eb_max_rpm_clutch_DC)

{

output_clutch_DC = eb_max_rpm_clutch_DC)                ‘limit output

                    }

}

 


Regime B (For higher speeds, where binding would not be noticed, and the transmission to likely be in D or OD when off-throttle)

Step 1: Determine what rpm to start applying engine braking DC for a given speed

start_apply_rpm = f[vehicle_speed)

Step 2: Determine what clutch to output for the given rpm

output_clutch_DC = f[start_apply_rpm, rpm]

If (rpm £ start_apply_rpm)

{

output_clutch_DC = 0                                        ‘No response for low rpm

}

else

{

if (output_clutch_DC  > eb_max_rpm_clutch_DC)

{

output_clutch_DC = eb_max_rpm_clutch_DC)                ‘limit output

                    }

}

                                                Range /

Calibratibles                                (Resolution)                      Definition

eb_enable                                                                     Boolean                                                                                Enables strategy when true

eb_start_apply_clutch_DC                                                                              DC at min rpm where clutch is engaged

eb_ma...